1. Field of the Invention
The present invention relates to an ignition system, and more particularly to one which provides direct ignition on a plurality of cylinders.
2. Description of the Prior Art
A car ignition system (as shown in FIG. 4) used at the present time is an indirect ignition system which has a high voltage ignition coil 86 electrically connected to a central pole of a distributor 85 via a high voltage output cable 861. The distributer 85 has a plurality of output terminals 851, 852, 853, and 854 respectively connected to a corresponding one of spark plugs SP1, SP2, SP3, and SP4. The central pole 850 of the distributer 85 is rotated in concert with the engine and thus is sequentially and repeatedly in electrical contact with the first output pole 851, the second output pole 852, the third output pole 853, and the fourth output pole 854 if the engine rotates. Each one of the spark plugs SP1, SP2, SP3, and SP4 is used to ignite a corresponding cylinder (not shown). The cylinders are sequentially and repeatedly ignited one by one by a corresponding spark plug which receives the ignition energy from a corresponding one of the output terminals of the distributer 85. However the energy for igniting all cylinders is merely from the high voltage ignition coil 86, therefore the ignition energy may be not enough for practical use, for example, when the engine is in high speed rotation, the ignition on each cylinder is in a relatively high frequency, which decreases the charging time period of the high voltage coil 86 thus also decreasing the ignition energy of each spark plug and causing ignition failure. Therefore, it can be seen that an indirect ignition system is apt to suffer ignition failure due to a relatively high speed of the engine. In FIG. 3, an available ignition system having a plurality of independent high voltage ignition coils for directly igniting a plurality of cylinders is illustrated. As shown in FIG. 3, a Hall sensor 91 connected to an engine cam of a car engine for detecting an angle status of the engine cam is electrically connected to a microcomputer 90. The microcomputer 90 receives an angle status signal from the Hall sensor 91 and continually outputs a driving signal from one of its four output terminals A, B, C, and D. Each output terminal A, B, C, and D is respectively connected to a corresponding power transistor 92 which is further connected to a corresponding high voltage coil 93. Each high voltage coil 93 is connected to a spark plug 94 for providing ignition energy to energize the latter to ignite a corresponding cylinder. Since a driving signal is continually outputted from one of the four output terminals A, B, C, and D, the power transistors 92 are turned on/off in rotation according to the output status of the output terminals A, B, C, and D, thus causing the related high voltage coil 93 to induce high voltage to energize the related spark plug to ignite the corresponding cylinder. The ignition system as shown in FIG. 3 is a direct ignition system, yet the structure thereof is quite different from the indirect ignition system as shown in FIG. 4 which employs a distributer. Additionally, the Hall sensor 91 of the direct ignition system is merely suitable to some engines which are physically mated with the Hall sensor, thus the conventional indirect ignition system is difficult to be modified to the direct ignition system as shown in FIG. 3.
It is requisite to provide a new ignition system which easily transforms the conventional indirect ignition system to direct ignition system.